The European athletics championships run from June 27 to July 1. Heats for the Olympic 400 metres begin five weeks later.
The Borlee's coach and father Jacques, himself a former Belgian champion sprinter, said that the Helsinki event would involve five 400 metres races when the relay was included.
"You need two or three weeks to be able to recover and to renew training and to arrive at the Olympics that's not possible," he told Reuters television on the sidelines of a news conference in Brussels.
Kevin, who won the title two years ago in a time of 45.08 seconds, will still run the relay. Jonathan, who fniished fifth in Daegu in 2011 and third in the European championships in 2010, may well drop down to the 200 metres.
"What is important is that he does the 200 metres in a relaxed way, without a sense of trying for a medal and with the goal of improving for the Olympics where he will be in the 400 metres," Jacques said.
Kevin said he had some regrets at not defending his European title, but accepted it was inevitable.
"I'd like to have defended my title and be able to participate in the European championships, but it's an Olympic year and the objective is the Olympic Games. So you have to make a choice," he said.
Jacques, who also coaches the 4x400 metre relay team and is a big figure in Belgian athletics, believes the European championships needs a revamp.
His view is that it should be held every year with trials taking place two weeks before the event proper, leaving just the semifinals and final for individual events and only the final for the relay.
He argues it would be better for athletes and for the spectators.
Tuesday's news conference served to summarise training to date in the United States and the programme of events for the rest of the season, also including Olivia Borlee, whose focus is the 200 metres.
The plans for 24-year-old Kevin and Jonathan are very different and they will only face each other once, over 400 metres in Monaco on July 20, before the Olympics.
Jacques explained that was partly because, while they were twins, they were different physically and mentally.
"Kevin weighs two kgs more. Jonathan has more of a pulling stride, while Kevin pushes more," he said.
"Mentally, Kevin has a strategy of putting all the stones in place and when they are all in place he can perform. It takes more time. Jonathan, when he feels good, he is a killer and can reach an exceptional performance more rapidly than Kevin."
Both are likely to face keen competition from defending Olympic champion LaShawn Merritt and world champion Kirani James as well as American Jeremy Wariner.
"It's difficult to say a month and a half before the Olympic Games. You could get to 44.50 or 44.40 seconds or better, but then if you have five others ahead of you the time doesn't mean so much," Kevin said.